Nuclear Winter

Nuclear Winter. Although there had been earlier antecedents, the widespread public debate about nuclear winter began in 1982 with the suggestion by Paul Crutzen, at the University of Colorado, and John Birks, at the Max Planck Institute, that a large‐scale nuclear war could produce such conflagrations of forests that a smoke pall covering perhaps half the northern hemisphere would develop. This would absorb enough of the light from the Sun that there could be serious and prolonged reductions in photosynthesis and in temperatures over that part of the planet, resulting in catastrophic agricultural failure. The work was quickly picked up by R. P. Turco, O. B. Toon, T. P. Ackerman, J. B. Pollack, and Carl Sagan, who, on the basis of quantitative modeling, concluded that a large‐scale nuclear war could be expected, mainly as a result of the burning of cities rather than forests, to cause temperatures to drop by 36° C. (65° F.) and to remain below freezing for several months. Their work, commonly referred to as the TTAPS study, provided the basis for a number of other publications that appeared in the next three years bearing Sagan's name and the appellation “nuclear winter,” which he and Turco coined to describe the phenomenon.

Not surprisingly, these publications caused a considerable stir, given their wide circulation and some of the apocalyptic visions presented: that a major nuclear exchange would produce “the greatest biological and physical disruption of the planet in its last 65 million years” (a period that included the four great ice ages) and that the number of survivors would be reduced to prehistoric levels (presumably a fraction of 1% of those now alive). All of this was buttressed by claims that the TTAPS results were insensitive to wide variations in assumptions about parameters used in modeling. In fact, the results were anything but robust, as subsequent studies would make clear.

There were basically two kinds of problems. First, TTAPS was based on the simplifying assumption that the burning of cities would produce an instantaneous homogeneous distribution of smoke over the entire northern hemisphere, when in reality it would take some days for such spreading to occur, during which time much of the smoke would likely be removed by natural processes. Moreover, the modeling took no account of the warming effects of the infusion of relatively warm air from oceanic and tropical areas to continental interiors. More refined later modeling that did take account of these phenomena, and used comparable assumptions about amounts and characteristics of the smoke from fires, led to radically smaller temperature effects.

Second, there were a number of uncertainties in key areas which, if resolved, could plausibly lead at one extreme to no significant climatic effects, or at the other, to effects as dire as those discussed in 1983, a range of outcomes largely conceded by Turco and Sagan in a characterization of five different classes of nuclear winter by 1989.

The nuclear winter controversy was perhaps as much about policy as about geophysics. Advocates of enlarged programs for deterrence of nuclear attacks and for defense against them seized on the possibility of nuclear winter to buttress their case for such programs. In contrast, the most vocal proponents of the nuclear winter theory generally argued that it strengthened the case for reducing nuclear stockpiles and foregoing the development and acquisition of new nuclear weapons; and some argued that even if there were doubts about the phenomenon, it would be wise to base policy on “worst‐case analysis.” Others argued that war involving enough nuclear explosions to trigger nuclear winter would likely have consequences so catastrophic, at least for the nuclear weapons states, as to overshadow the possibility of nuclear winter in concerns about policy. (And some of those skeptical about the more dire prognostications warned particularly against worst‐case analysis being used as a basis for mitigative actions by countries not likely to be directly attacked, noting that such actions could well involve the use of scarce resources sorely needed for other purposes.)

By the early 1990s, nuclear winter was no longer a salient issue in geophysics or from a policy perspective, very likely because the geophysical case for it seemed so questionable; because the initiation of massive oil fires in Kuwait during the Persian Gulf War did not lead to significant climatic effects, as some had predicted; and probably most important, because concern about large‐scale nuclear attacks had largely dissipated with the end of the Cold War.[See also War Plans.]

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Nuclear Winter

Encyclopedia of Espionage, Intelligence, and Security
COPYRIGHT 2004 The Gale Group Inc.

Nuclear Winter

█ AGNES GALAMBOSI

Nuclear winter is a meteorological theory estimating the global climatic consequences of a nuclear war—or a natural disaster such as a major asteroid impact—that injects large amounts or dust or water vapor into the atmosphere. Nuclear winter models predict prolonged and worldwide cooling and darkening caused by the blockage of sunlight.

During the Cold War, concern about the use of nuclear weapons initially concentrated on initial blast damage and the dangers of radioactive fallout. Subsequently, researchers began to explore the possible environmental effects of nuclear war. The term nuclear winter was first defined and used by American astronomer Carl Sagan (1934–1996) and his group of colleagues in their 1983 article (later referred to as the TTAPS-article, from the initials of the authors' family names). This article was the first one to take into consideration not only the direct damage, but also the indirect effects of a nuclear war.

During a nuclear war, the exploding nuclear warheads would create huge fires, resulting in smoke and soot from burning cities and forests being emitted into the troposphere in vast amounts. According to nuclear winter theory, this would block the Sun's incoming radiation from reaching the surface of Earth, causing cooling of the surface temperatures. The smoke and soot soon would rise to high altitude because of their high temperature and drift there for weeks without being washed out. Finally, the particles would settle in the Northern Hemisphere mid-latitudes as a black particle cloud belt, blocking sunshine for several weeks.

The ensuing darkness and cold, combined with nuclear fallout radiation, would kill most of Earth's vegetation and animal life, which would lead to starvation and diseases for the human population surviving the nuclear war itself. At the same time, because the smoke would absorb sunlight, the upper troposphere temperatures would rise and create a temperature inversion causing further retention of smog at the lower levels. Another predicted consequence is that nuclear explosions would produce nitrogen oxides that would damage the protective ozone layer in the stratosphere and allow more ultraviolet radiation to reach Earth's surface.

Although the basic findings of the original TTAPS-article have been confirmed by later reports and sophisticated computer modeling, some later studies report a lesser degree of cooling that would last for weeks instead of the initially estimated months. In the extreme, however, depending on the number of nuclear explosions, their spatial distribution, targets, and many other factors, a cloud of soot and dust could remain for many months, reducing sunlight almost entirely and decreasing average temperatures to well below freezing over a majority of the densely inhabited areas of the Northern Hemisphere.

The nuclear winter scenario remains scientifically controversial because the exact level of atmospheric damage, along with the extent and duration of subsequent processes cannot be agreed upon with full confidence. Opponents of the nuclear winter theory argue that there are many problems with the hypothesized scenarios either because of the model's incorrect assumptions (e.g., the results would be right only if exactly the assumed amount of dust would enter the atmosphere, or because the model assumes uniformly distributed, constantly injected particles). Other critics of the nuclear winter scenario point out that the models used often do not include processes and/or feedback mechanisms that may moderate or mitigate the initial effects of nuclear blasts on the atmosphere (e.g., the moderating effects of the oceans). In contrast to nuclear winter models, some climate models actually postulate a "nuclear summer," resulting from a worldwide warming caused by many small contributions to the greenhouse effect from carbon dioxide, water vapor, ozone, and various aerosols entering the troposphere and stratosphere.

What all scenarios and models forecast, however, is that a nuclear war would have a significant effect on the atmosphere and climate of Earth. This in turn would drastically and negatively affect many aspects of life such as food production and energy consumption.

█ FURTHER READING:

BOOKS:

International Seminar on Nuclear War and Planetary Emergencies, 20th Session: The Role of Science in the Third Millennium, Man-Made & Natural Disasters, Post-Berlin-Wall Problems-Nuclear Proliferation in the Multipolar World.Singapore: World Scientific Publishing, 1997.

Weinberger, Casper. "The Potential Effects of Nuclear War on the Climate." Nuclear Winter, Joint Hearing before the Committee on Science and Technology and the Committee on Interior and Insular Affairs, U.S. House of Representatives. Washington, D.C.: Government Printing Office, 1985.

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Nuclear Winter

World of Earth Science
COPYRIGHT 2003 The Gale Group, Inc.

Nuclear winter

Nuclear winter is a theory estimating the global climatic consequences of a nuclear war: prolonged and worldwide cooling and darkening caused by sunlight-blocking smoke and soot entering the atmosphere. During the Cold War after World War II, the concern about nuclear weapons was increasing all over the world. Initially, only the danger of radioactive fallout was recognized, but later also the possible environmental effects of a nuclear war became the subject of several studies. The term nuclear winter was first defined and used by American astronomer Carl Sagan (1934–1996) and his group of colleagues in their 1983 article (later referred to as the TTAPS-article, from the initials of the authors' family names). This article was the first one to take into consideration not only the direct damage, but also the indirect effects of a nuclear war.

The basic assumption during a nuclear war is that the exploding nuclear warheads would create huge fires, resulting in smoke and soot from burning cities and forests being emitted into the troposphere in vast amounts. This would block the sun's incoming radiation from reaching the surface of Earth, causing cooling of the surface temperatures. The smoke and soot soon would rise because of their high temperature , allowing them to drift at high altitudes for weeks without being washed out. Finally, the particles would settle in the Northern Hemisphere mid-latitudes as a black particle cloud belt, blocking sunshine for several weeks. The darkness and cold, combined with nuclear fallout radiation, would kill most of Earth's vegetation and animal life, which would lead to starvation and diseases for the human population surviving the nuclear war itself. At the same time, the upper troposphere temperatures would rise because the smoke would absorb sunlight and warm it up, creating a temperature inversion, which would keep smog at the lower levels. Another possible consequence is that nuclear explosions would produce nitrogen oxides, which would damage the protective ozone layer in the stratosphere , thus allowing more ultraviolet radiation to reach the earth's surface.

Although the basic findings of the original TTAPS-article have been confirmed by later reports, some later studies report a lesser degree of cooling would occur, only around 25 degrees of temperature drop and only for weeks instead of the initially estimated months. According to different scenarios, depending on the number of nuclear explosions, their spatial distribution, targets, and many other factors, this cloud of soot and dust could remain for many months, reducing sunlight almost entirely, and decrease average temperatures to as low as −40°C in the Northern Hemisphere continents. There are other studies, that mention the possibility of a not so severe nuclear winter as originally estimated, hence it is named a nuclear fall. Other researchers even talk about nuclear summer, stating that a worldwide warming would follow a nuclear war because of the many small contributions to the greenhouseeffect from carbon dioxide, water vapor, ozone , and various aerosols entering the troposphere and stratosphere. What all scenarios agree on is that a nuclear war would have a significant effect on the atmosphere and climate of the earth and, consequently, many aspects of life such as food production or energy consumption would be drastically effected.

Opponents of the nuclear winter theory argue that there are many problems with the hypothesized scenarios either because of the model's incorrect assumptions (e.g., the results would be right only if exactly the assumed amount of dust would enter the atmosphere, or the model assumes uniformly distributed, constantly injected particles), or because important effects, processes and/or feedback mechanisms are not taken into consideration (e.g., the moderating effects of the oceans , or small-scale processes are not included, or the biological effects are not addressed), or simply because there are many uncertainties involved in the estimates. The topic even at present day remains controversial, because the exact level of damage, along with the extent and duration of the effects, cannot be agreed upon with full confidence.

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nuclear winter

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

nuclear winter, theory holding that the smoke and dust produced by a large nuclear war would result in a prolonged period of cold on the earth. The earliest version of the theory, which was put forward in the early 1980s in the so-called TTAPS report (named for last initials of its authors, Richard P. Turco, Owen B. Toon, Thomas P. Ackerman, James B. Pollack, and Carl Sagan), held that the ensuing low temperatures and prolonged periods of darkness would obliterate plant life and seriously threaten the existence of the human species. Later models, which took into account additional variables, confirmed the basic conclusions of the TTAPS report and suggested that the detonation of 100 megatons (the explosive power of 100 million tons of TNT) over 100 cities could produce temperature drops ranging from 5 to 15 degrees.

Cite this article Pick a style below, and copy the text for your bibliography.

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